中国邮电高校学报(英文) ›› 2012, Vol. 19 ›› Issue (5): 66-76.doi: 10.1016/S1005-8885(11)60302-6
敖乃翔1,徐赢颖1,陈常嘉2,黄琰3
AO Nai-xiang, XU Ying-ying, CHEN Chang-jia
摘要：
Internet Service Providers (ISPs) have taken some measures to reduce intolerable inter-ISP peer-to-peer (P2P) traffic costs, so that user experiences of various P2P applications have been affected. The recently emerging Offline downloading service seeks to improve user experience by using dedicate servers to cache requested files and provide high-speed uploading. However, with rapid increase in user population, the server-side bandwidth resource of Offline downloading system is expected to be insufficient in the near future. We propose a novel complementary caching scheme with the goal of mitigating inter-ISP traffic, alleviating the load on servers of Internet applications and enhancing user experience. Both architecture and caching algorithm are presented in this paper. On the one hand, with full knowledge of P2P file sharing system and Offline downloading service, the infrastructure of complementary caching is designed to conveniently be deployed and work together with existing platforms. The co-operational mechanisms among different major components are also included. On the other hand, with in-depth understanding of traffic characteristics that are relevant to caching, we develop complementary caching algorithm with respect to the density of requests, the redundancy of file and file size. Since such relevant information can be real-time captured in our design, the proposed policy can be implemented to guide the storage and replacement of caching unities. Based on real-world traces over 3 months, we demonstrate that the complementary caching scheme is capable to achieve the “three-win” objective. That is, for P2P downloading, over 50% of traffic is redirected to cache; for Offline downloading, the average server-dependence of tasks drops from 0.71 to 0.32; for user experience, the average P2P transfer rate is increased by more than 50KB/s.
